The present invention relates generally to welding systems and, more particularly, to a welding arc termination procedure and control.
During a welding process, a weld power is generated by a power source and is communicated to a weld site via a torch. A shielding gas is also communicated to the weld site and shields a weld pool from environmental contaminants. The environmental contaminants include air and its constituents such as water vapor and oxygen. Exposure of the molten weld material to the contaminants detrimentally affects weld quality. The interaction between the contaminants and the material of the weld is, in part, temperature dependent. Accordingly, it is desirable to maintain the flow of the shielding gas after an arc termination until the weld has cooled such that the material of the weld is non-reactive with the environmental contaminants.
Frequently, when an operator desires to terminate a welding process, the operator releases the torch trigger which nearly instantaneously terminates the weld arc and the flow of shielding gas. Although such arc termination expeditiously terminates the weld process, such termination results in an unsatisfactory weld discontinuity at the point of weld termination. During welding arc termination, a gradual reduction in weld power in conjunction with continued flow of shielding gas improves the quality of the weld at the weld termination.
Welding devices with arc termination control which provide for the gradual reduction of weld power and the continued flow of shielding gas generally require operator actuation of a switch to initiate the arc termination sequence. Commonly, the torch includes a switch that is separate from the torch trigger which, when activated, causes the power source to provide the gradual reduction of weld power and continued shielding gas flow. Alternatively, a foot pedal can be provided which actuates the arc termination procedure. Although such devices provide improved arc termination control, they are not without drawbacks.
The extraneous switching means require operator actuation and are ill equipped to tolerate a dynamic welding environment. When an operator is focused on a welding process, the operator occasionally loses the relative position of the torch positioned or foot pedal switching means. Wearing the protective apparel associated with the welding process, the operator can have difficulty locating the pedal when arc termination is desired and thereby terminates the weld process without actuation of the weld termination procedure. Additionally, operator manipulation of the components associated with the welding process inhibits the operator's degree of freedom of motion. Particularly during gas tungsten arc welding (GTAW), wherein the operator is commonly required to position the torch relative to the workpiece with one hand and feed the consumable material with the other hand, the operator is ill-equipped to manually actuate a switch to actuate the weld termination procedure.
Other welding-type devices have automated the means for initiating the weld termination procedure but suffer from alternate drawbacks than those mentioned above. One such system has a feedback feature which monitors a parameter of the weld process and actuates the weld termination procedure responsive to the feedback signal. Prior to initiation of a welding process, an operator must preset a plurality of arc threshold values. During the welding process, when one of the thresholds is crossed a first time, a termination sequence is enabled, and when the threshold is crossed a second time, or a second threshold is crossed, the termination procedure is then actuated. Although such a termination procedure reduces the number of operator steps needed to actuate the arc termination procedure during welding, this weld termination procedure still does not minimize the steps for most efficient operation.
The arc parameters associated with the weld process are affected by the amount of power required for a desired weld process, a length and size of weld cable between the power source and the torch, condition of the weld cable, size and type of the consumable material, desired arc length, and operator skill. Understandably, these are but a few of the variables which affect the value of the monitored arc parameter. The operator must account for each of these parameters when setting the plurality of arc threshold values which initiate and actuate the arc termination procedure. This becomes particularly problematic with novice or minimally experienced operators who may be unaware of the effect of any of the variables on the monitored parameter. That is, an operator unfamiliar with a particular welding system or the requirements of a desired welding process can inadvertently set the threshold values at a value that cannot be achieved during the welding process. Such a configuration results in inoperability of the weld termination procedure. Conversely, if the operator sets the thresholds within a range of normal weld arc performance, the weld termination procedure is initiated and activated prematurely.
In addition to the operating issues addressed above, even when the operator appreciates the interrelation of the all of the variables associated with the threshold, presetting the thresholds is a time consuming and tedious process. In a dynamic work environment, an operator is required to transition from one welding process to another. The variable parameters between the welding processes are not always the same. As such, the operator is required to reset the thresholds for different welding process or forgo utilization of the weld termination procedure. If the operator elects to reset the thresholds, process efficiency decreases as the welding apparatus is idle until the thresholds are reset and weld quality is sacrificed if the operator elects to circumvent the weld termination procedure.
It would therefore be desirable to have a system and method capable of automatically actuating a weld termination procedure and which is dynamically responsive to different weld processes.